In general, dynamic display devices operate by scrolling a display medium on which at least two, and more generally three, different notices have been printed. This canvas is wound in one direction then the other, and is regularly immobilized so that the printed notice is displayed correctly when viewed from the outside.
In a first family of scrollable devices, the display medium consists of a canvas onto which various paper notices are bonded. This canvas is wound onto motorized rollers, thus causing the paper notices to be wound up. It will be understood that this first solution may cause wrinkling when the canvas is wound, and these wrinkles may in turn cause the system to jam and therefore interrupt the correct displaying.
An improvement to this type of device was described by the applicant in document WO 00/67243. The display device described in that document comprises rollers onto which and from which a canvas bearing printed information is wound. To ensure optimum winding, the information-bearing canvas is kept under transverse tension as it is unwound. This maintaining of transverse tension also keeps the notice nice and flat, giving it a good appearance.
In order to maintain transverse tension in this way, the information-bearing canvas has lateral edges equipped with a rod able to slide in sideways that are fixed with respect to the scrolling device.
The display medium used may for example be a film of slightly extensible plastic that has been printed. More specifically, several successive notices are printed one after the other onto this canvas.
In practice, the scrollable devices are fed with information-bearing canvases according to the lengths of the display campaigns. Now, for certain products and certain advertisers, it may be that the periods are not the same for the various notices present on the same canvas. Hitherto it has been necessary to replace the entirety of a canvas even if just one of the notices needs to be replaced. That then entails a further operation of printing the notices which are not replaced but carried forward over successive periods. This is necessary in particular in order to maintain a one-piece structure as regards the lateral edges, which need to be continuous in order to slide correctly in the sideways that laterally guide and maintain transverse tension.
It will be appreciated that these printing operations are unnecessary because they consume quantities of canvas and printing resources in order to produce notices that have already been printed.
The problem that the invention sets out to solve is that of making it possible to optimize successive display campaigns by customizing the various notices while at the same time remaining compatible with installation in devices that maintain transverse tension, particularly through the use of lateral rods.